title: Reinvestigation of the oxidative folding pathways of hen egg white lysozyme: switching of the major pathways by temperature control.
abstract: It has been well established that in the oxidative folding of hen egg white lysozyme (HEL), which has four SS linkages in the native state (N), three des intermediates, i.e., des[76-94], des[64-80], and des [6-127], are populated at 20 °C and N is dominantly formed by the oxidation of des[64-80] and des[6-127]. To elucidate the temperature effects, the oxidative folding pathways of HEL were reinvestigated at 5-45 °C in the presence of 2 M urea at pH 8.0 by using a selenoxide reagent, DHSox. When reduced HEL was reacted with 1-4 equivalents of DHSox, 1S, 2S, 3S, and 4S intermediate ensembles with 1-4 SS linkages, respectively, were produced within 1 min. After the oxidation, 3S was slowly converted to the des intermediates with formation of the native structures through SS rearrangement. At 5 °C, des[76-94] was populated in the largest amount, but the oxidation to N was slower than that of des[64-80] and des[6-127]. At 35 °C, on the other hand, des[64-80] and des[6-127] were no longer stable, and only des[76-94] was populated. The results suggested that the major folding pathways of HEL can be switched from one to the other by temperature control.
authors.affiliation: Department of Chemistry, School of Science, Tokai University, Kitakaname, Hiratsuka-shi, Kanagawa 259-1292, Japan. miwaoka@tokai.ac.jp.
authors.forename: Kenta
authors.initials: K
authors.lastname: Arai
authors.forename: Wataru
authors.initials: W
authors.lastname: Shibagaki
authors.forename: Reina
authors.initials: R
authors.lastname: Shinozaki
authors.forename: Michio
authors.initials: M
authors.lastname: Iwaoka
mesh_terms: D000818:Animals; D002645:Chickens / Q000378:metabolism; D004220:Disulfides / Q000737:chemistry; D004529:Egg White; D005260:Female; D007700:Kinetics; D009113:Muramidase / Q000737:chemistry; D010084:Oxidation-Reduction; D011489:Protein Denaturation; D017510:Protein Folding; D012259:Ribonuclease, Pancreatic; D013696:Temperature
chemical_list: D004220:Disulfides; D012259:Ribonuclease, Pancreatic; D009113:Muramidase